The bench press is an effective exercise for developing the front side of your upper body. This exercise becomes even more effective if you raise your legs during your sets, so your feet do not make contact with the floor. Spanish exercise scientists, affiliated with the Universidad de Almeria, report this in PLoS One.

Study
The researchers had 20 young men bench press several times. On one occasion the men placed their feet flat on the floor, the other time they lifted their legs.

The researchers had attached electrodes onto the skin of the test subjects with which they could measure the activity of the muscles under the electrodes. This way the researchers could see how hard those muscles had to work.

Results
Raising the legs during the bench press increased the activity of all the muscles involved. The pecs, the delts, the triceps and even the muscles in the forearms worked significantly harder if the subjects had raised their legs.

Conclusion
"To perform the bench press exercise with flexed hips could be recommended for training in sports where the upper limbs and hip flexor muscles are required", schrijven de onderzoekers.

"However, more studies are needed to analyze the influence of hip flexor muscle activation on lumbar spine stress in the bench press exercise."